Laser therapy (fiberoptically-directed monochromatic UVB light) targets only psoriatic plaques. This allows much more aggressive phototherapy as compared to traditional ultraviolet B and oral psoralen with ultraviolet A , which exposes non-involved skin as well as psoriatic skin to UV light. With aggressive excimer laser therapy, it is well known that psoriasis can improve significantly or clear in approximately ten sessions instead of the 30 to 40 sessions needed with regular full-body phototherapy to achieve clearance of the skin. This dramatic difference is attributed to the fact that psoriatic lesions are able to withstand a much higher dose of light than non-involved skin. Excimer laser therapy dosing is determined by the maximum tolerance of psoriatic skin whereas full body UV therapy dosing is determined by the MED (minimal erythema dose) of non-involved skin. Delivery of higher doses subsequently results in faster clinical response and much greater clinical efficacy. Hence, the new supra-erythemogenic phototherapy strategy results in a fewer number of sessions needed for clearance ( ). The supra-erythemogenic phototherapy strategy involves delivering UVB at a dose much greater than the minimal erythema dose (MED) (2). MED is the traditional limit on how aggressively non-laser phototherapy can be conducted (UVB doses beyond the MED will burn the patient).